Undernutrition is associated with mortality, exacerbation, and poorer quality of life in patients with chronic obstructive pulmonary disease: A systematic review with meta‐analysis of observational studies

Impaired nutrition status is recognized as a risk factor for worse clinical outcomes in patients with chronic obstructive pulmonary disease (COPD). The aims of this study were to investigate how undernutrition is diagnosed, its prevalence, and whether there is an association between this condition and clinical outcomes in patients with COPD. The search for this systematic review of observational studies (PROSPERO: CRD42020191888) was performed in the PubMed, Embase, and Scopus databases, with no date or language restrictions. The studies had to report data on the diagnosis of undernutrition and its association with mortality, exacerbation, length of hospital stay, or quality of life in adult patients with COPD. A meta-analysis with a random-effects model was performed to combine data. Forty-nine studies were included (20 of them classified as having a low risk of bias), and the most common diagnostic method of undernutrition was body mass index (BMI) (n = 36). The pooled prevalence of undernutrition was equal to 20% (95% CI, 0.15-0.25; I² = 100%), and it was associated with mortality (risk ratio = 1.97; 95% CI, 1.55-2.50; I² = 98%), exacerbation (risk ratio = 1.73; 95% CI, 1.03-2.91; I² = 96%), and poorer quality of life (mean difference = 8.25; 95% CI, 5.40-11.10; I² = 79%). For all outcomes, the certainty of evidence was very low. In conclusion, undernutrition is prevalent and is associated with poorer outcomes in patients with COPD. However, undernutrition is mainly diagnosed by BMI, which underreports its prevalence, and the certainty of the evidence is very low.